Conventionally, for the purpose of developing functional materials, a variety of polymeric materials have been produced industrially, such as rubber materials, resin materials, and the like. On the other hand, the growth of the polymer industry has brought about mass production and consumption of general-purpose materials, and the processing of polymer waste is a crucial problem that needs to be solved as soon as possible. In order to solve this problem, technological progress in the reuse, recycling, and the like of polymeric materials is essential. For example, along with the spread of motorization, tires made from a rubber material are now mass produced and mass consumed as an essential automobile component, yielding an enormous number of used tires. Research into recycling and effective utilization of used tires has thus been promoted, and in particular the recovery of usable material has become a major issue. For example, JP8-027394A (PTL 1) discloses a method for producing carbon black by thermal decomposition or incomplete combustion of organic waste such as waste tires.
The carbide obtained by thermal decomposition or incomplete combustion of polymer waste normally includes matter other than hydrocarbons, and therefore unlike the carbon material which is obtained by thermal decomposition or incomplete combustion of hydrocarbons and which is formed nearly entirely from carbon (i.e. carbon black in the original sense), this carbide does not exhibit a sufficient reinforcing effect with respect to a rubber composition at the time of combination with rubber. Hence, room for improvement remained in the recovery and effective utilization of the value offered by polymer waste.
Therefore, JP2010-141099A (PTL 2) discloses a method for obtaining carbon material for reinforcing rubber by mixing a carbide with carbon black, the carbon material having a sufficient reinforcing effect even when combined with rubber components despite the inclusion of a carbide conventionally considered to have a weak reinforcing property for rubber.